Types of urine specimens:
Over the course of a 24-hour period, the composition and concentration of urine changes continuously. For this reason, various types of specimens may be collected, including:
The first voided morning specimen is particularly valuable because it is more concentrated and abnormalities are easier to detect. An early morning specimen is also relatively free of dietary influences and changes due to physical activity. In collecting any urine specimen, it is always important for the nurse to observe specific agency protocols, to check with the laboratory regarding the need for refrigeration or preservation of specimens, and to follow universal precautions. Single random specimens may be taken at any time of the day or night. Timed specimens range from short-term 2-hour collections to 24-hour collections.
A 24-hour urine specimen is an extremely important diagnostic test because it reveals how the kidney adjusts to changing physiologic needs over a long period. Substances excreted by the kidney are not excreted at the same rate or in the same amounts during different periods of day and night; therefore, a random urine specimen does not accurately represent the processes taking place over a 24-hour period. However, a 24-hour urine specimen is useful only when all the patient's urine is collected for 24 hours. Even if just one sample is discarded, the results will be inaccurate. The nurse must ensure that the patient and all assistive personnel understand the importance of saving all the urine. To begin the 24-hour collection, the person voids and discards the urine already in the bladder. All urine starting with the next voiding is collected for the next 24 hours and put into a large collection bottle. To prevent breakdown of urinary components, the collection has a preservative added to it or is refrigerated.
Collection of specimens:
The laboratory needs at least 10 ml of urine for a routine UA. The perineal area in women or the end of the penis in men should be cleaned before the urine is collected. For a female, collecting midstream urine lessens the contamination from vaginal secretions or menstrual flow. Wiping the genitalia with a sterile wipe may stimulate the voiding reflex in infants. Various collection bags can be also be attached to the genitalia of infants or small children. A cotton ball in a diaper can be used for quick collection of urine for dipstick testing. If a culture and sensitivity are to be completed in addition to the routine UA, the urine specimen must be placed in a sterile container. Urine specimens need to be examined within 2 hours. Urine that is left to standing too long becomes alkaline because bacteria begins to split the urea contained in urine into ammonia. Visualization of urine and other tests are inaccurate if the pH of the urine specimen has become highly alkaline. A urine specimen should be refrigerated if it cannot be sent to the laboratory within 2 hours.
Reference values for normal urinalysis (It is important to check with your agency's laboratory for normal reference values.)
General characteristics and measurements:
Chemical determinations:
Microscopic exam of sediment: